@inproceedings{audun1992zak's,
title={Zak's theorem on superadditivity},
author={Audun Holme, and Joel Roberts},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203542443535617},
booktitle={Arkiv for Matematik},
volume={32},
number={1},
pages={99-120},
year={1992},
}